DIFFERENTIATION OF PARTIALLY MESODERMALIZED ECTODERM; HOMOIOGENETIC AND HETEROGENETIC INDUCTION BY PRIMARILY INDUCED PART OF THE ECTODERM

Using embryos of the Japanese newt, Cynops pyrrhogaster , homoiogenetic and heterogenetic induction were investigated in the partially mesodermaelzed presumptive ectoderm. Half of the isolated presumptive ectoderm was placed in contact with the swimbladder of the crucian carp, Carasius auratus , for 15 or 60 min, while the other half was stained with Nile blue sulfate at the same time. The distribution of the stained cells in the tissues evoked in the explants was examined after cultivation for 10 days.
Some mesodermal tissues were composed of both stained and unstained cells. This indicates homoiogenetic induction by the primarily induced part of the ectoderm on the other half. The neural and epidermal tissues in the explants were composed of stained cells only, except in one case. We conclude that the neural tissues are derived from cells not placed in contact with the swimbladder and that they are induced by the primarily induced part of the ectoderm.     

Paedomorphosis in the Turonian (Late Cretaceous) collignoniceratine ammonite lineage from the north Pacific region

Ontogenetic development and variation of shell ornament of the four Turonian collignoniceratine ammonites, Collignoniceras woollgari (Mantell 1822), Subprionocyclus neptuni (Geinitz 1850), S. normalis (Anderson 1958) and S. minimus (Hayasaka & Fukada 1951) have been compared on the basis of large population samples from Hokkaido (Japan), California and the US Western Interior Province. Our study revealed that the ornament types observed in the early-middle stage of C. woollgari occur in the middle-late stage of the three other species, and that those in the early-middle stage of S. neptuni appear in the middle-late stage of S. normalis and S. minimus. These species are generally regarded as closely related phylogenetically, because they share several common morphological features such as the presence of double ventrolateral tubercles and a serrated keel. If a postulated phylogeny starting from C. woollgari to S. normalis and S. minimus via S. neptuni is accepted, the mode of morphological evolution in the lineages can be explained by paedomorphosis. Available palaeobiogeographical data suggest that this paedomorphic evolution occurred independently on the northwestern and northeastern sides of the northern Pacific, where the C. woollgari – S. neptuni – S. minimus, and C. woollgari – S. neptuni – S. normalis sublineages evolved.     

PHOSPHOLIPIDS IN THE BOVINE TONGUE PAPILLAE

Lipids, especially phospholipids in the bovine tongue papillaeand the surrounding epithelium were analyzed with a view toexamine the role of phospholipids in the taste reception. Thetaste buds bearing papillae, the circumvallate and the fungiformpapillae showed much higher phospholipid content than thoseof the filiform papillae bearing no taste buds and those ofthe epithelium. Nine phospholipids in the papillae and epitheliumwere identified and quantified. It was shown that the main componentsof phospholipids were phosphatidylcholine, phosphatidylethanolamine,sphingomyelin and phosphatidylserine. The composition of phospholipidsin the papillae bearing taste buds was not appreciably differentfrom that in the filiform papillae and the epithelium. On thebasis of the obtained results, the role of lipid in taste receptionis discussed.     

Analysis of a Carboniferous embryonic ammonoid assemblage implications for ammonoid embryology

An embryonic ammonoid assemblage was discovered in a carbonate concretion recovered from a dysoxic, relatively offshore marine shale of Virgilian (Upper Pennsylvanian) age in Kansas, USA. The assemblage consists primarily of two species of the Goniatitina, Aristocerassp. and Vidrioceras sp., whose initial chambers (protoconchs) differ in size and shape. Microscopic observations of serial thin sections of specimens at different growth stages reveal the sequence of embryonic shell development starting with the formation of the initial chamber and ending with the synchronous secretion of a prismatic proseptum and nacreous swelliig (primary varix) at the aperture. The mode of occurrence of the embryonic shells of the two species in the concretion suggests that these ammonoids produced numerous small offspring, a reproductive strategy similar to that in many extant coleoids. □ Ammonoids, embryonic shells, development, Carboniferous, Kansas.     

Transmission of Homoiogenetic Induction in Presumptive Ectoderm of Newt Embryo

Using newt, Cynops pyrrhogaster , embryos, the production and/or transmission of a homoiogenetic effect of the induction within a presumptive ectoderm was investigated. The primary inductor was the swimbladder of a crucian carp, Caracius auratus. In the first experiment, a piece of presumptive ectoderm was isolated from an early gastrula and one-third of its inner surface was placed in contact with the swimbladder for 30 min. After removal of the inductor, the ectodermal piece was allowed to stand by itself for several hours (pre-cultivation), and then it was divided into three parts of equal size, i.e. the end that had been placed in contact with the swimbladder (P1), the next middle (P2) and the end part (P3).
The tissues produced in each part were examined after 10 days' cultivation in Holtfreter's solution. The induction was evoked not only in P1, but also in P2 and P3 which had been free from the inductor. The incidences of tissue differentiation in P2 and P3 increased with the lapse of the pre-cultivation time, and the rise in P3 came after P2. These results suggested that the mesodermal tissues in the parts not placed in contact with the swimbladder (P2 and P3) were evoked by the homoiogenetic stimulus which came from P1 and P2, respectively.
In the next experiment, P2 of the ectodermal piece was substituted by an aged ectoderm which had lost its primary competence. In this system, the mesodermal induction was not evoked in P3. This suggested that the production of the homoiogenetic activity of the ectoderm might be associated with its competenece.     

PHYSICOCHEMICAL STUDIES OF TASTE RECEPTION VI: Interpretation of Anion Influences on Taste Response

Monolayers of lipids from bovine tongue epithelium were preparedas a model system for the gustatory receptor membrane to clarifythe effects of anions on the taste response. Changes in thesurface potential of the monolayers were measured by use ofthe ionizing-electrode method under the presence of sodium andcalcium salts carrying various species of anions in the aqueousphase. The organic and chaotropic anions showed the suppressiveeffect on the surface potentials as compared with Cl^–or NO₃^-. The influences of anion species on the surface potentialwere similar to those on the taste response recorded from glossopharyngealnerve of the frog. This suggested that the effects of anionson the taste response could be explained in terms of the electricalpotential at the interface between the receptor membrane andstimulating solution. Analysis of data on the surface potentialrevealed that a conformational change of the monolayers causedby non-electrical interaction between the monolayers and anionsis responsible for the suppressive effect.